revert Charts version to 3.1.1

revert Charts version back to 3.1.1, because of bugs of Charts 3.2.0.
ChartsOrg/Charts#3673
ChartsOrg/Charts#3671

Some bug fixes.

Add stock k line example.

add support for linkage chart

add support for linkage chart.
Multiple charts can be synchronized at native side.

bug fix for setDataAndLockIndex.
swift 4.2 is required.

Support for Swift 4.2 and Xcode 10

Support for Swift 4.2 and Xcode 10.

Don't use if you are NOT using Swift 4.2

introduce setDataAndLockIndex

setDataAndLockIndex is important when you implement dynamic scroll chart.
Data is load in backend, and chart view remains unchanged.
Check examples-> infiniteScrollLineChart for detail.

fix Charts version to 3.1.1

bug fix

1. fix fitScreen for iOS
2. add missing properties for CombineChart
3. force chart.notifyDataSetChanged() for every setState, this can fix setting axisMinimum/axisMaximum without changing data, but slow down performance if setState is called frequently.

cocoapods is introduced and other improvements.

1. cocoapods support.
2. fix visibleRange
3. more settings for radar chart.
4. Add IndexValueFormatter. Now both axis and data support valueFormatter.
5. add highlights function
6. fix collision with react-native-maps

upgrade to MpAndroidChart 3.0.3 and Charts 3.1.1

Swift 4.1 is required for 0.4.3.

More attributes for PieChart and doc

#209 add x and y PieChartDataSet ValuePosition prop
#210 Fix chart frame being mispositioned
#217 Docs for react-native-charts-wrapper
#219 NormalizeSizeEnabled for Bubble Charts

Bug fix

Fix highlight in CombinedChart
Fix drawEntryLabels in PieChart
Add left, right, top, bottom in gesture callback.

Support gesture and direct function

Android and iOS gesture support.
Enable calling function on chart instance directly.